I recently upgraded the stock operational amplifier in the exhaust section of my Nakamichi 660 ZX tape deck by replacing it with a Burson V7 Classic op-amp, and the improvement in sound quality was immediate and profound. The moment I listened through the headphones, I was struck by how the soundstage expanded and deepened significantly. Vocals and instruments became far more distinct and palpable, while the overall dynamics and clarity of the audio were noticeably enhanced. As the sound continues to warm up, it becomes increasingly rich and natural, adding a remarkable depth to the listening experience. I am thoroughly impressed by this upgrade and will certainly be ordering more of these exceptional DACs.